If you've gone west, then just force yourself to stay up and 'sleep in' the next morning.

If you've come back, then change everything to suit your new timezone:
1. When you eat.
2. When you open and close the curtains.
3. When you wash and shower.
4. When you exercise (this one is really useful).
5. Try not to sleep for more than eight hours at a time.
6. Set your alarm, and make sure that you get up in the morning.
7. Don't ry to sleep if you're not tired. Read a book instead.